1. Field of the Invention
The present invention relates generally to a fluid pump unit, such as for a power source of an automotive power steering system.
2. Description of the Background Art
Such type of fluid pump is provided with an orifice at a discharge outlet for supplying working fluid to a power steering unit through the orifice. A flow control valve is associated with the orifice so that excessive flow rate of working fluid can be returned to the inlet of the pump. The flow control valve includes a pressure difference responsive valve spool which is responsive to a pressure difference between the upstream and downstream of the orifice. In the recent technology, there is proposed a fluid pump which has a flow control valve associated with a pressure relief valve for relieving excess pressure at the outlet of the orifice. Such type of fluid pump has been disclosed in Japanese Utility Model First (unexamined) Publication No. 60-64071, for example.
This pump conventionally proposed holds drawbacks. For instance, in order to establish communication between the pressure chamber in the pump and the spool chamber of the flow control valve, a fluid flow path has to be provided. This requires extra space in a pump housing. Furthermore, in the conventional construction, the flow control valve is protruded from the pump housing to increase the bulk size of the pump unit. In contrast to this, as can be appreciated, the engine room in the modern motor vehicle is filled with a quite great number of accessory parts to motivate a strong requirement for more compact construction of the fluid pump for easy installation.